UNDATED -- Intense searches for two people swept away from Northern California beaches by treacherous surf over the weekend have come up empty and both are feared to have drowned, according to authorities.

Petty Officer Jonathan Cilley, spokesman for the Coast Guard , said the first incident took place early Saturday when is 27-year-old Christopher Partridge was swept off the rocks at the beach at Limekiln State Park south of Big Sur. The Coast Guard spent all morning trying to locate Partridge before suspending the search at around noon.

With a water temperature of about 53 degrees, Cilley said, a person could only survive for around 4 1/2 to 5 hours.

At about the same time as the Big Sur search was being suspended an unidentified San Francisco resident was pulled into the turbulent waters off Gualala Point Regional Park while trying to rescue her dog.

Witnesses told authorities they saw the woman struggling in the surf around 11:30 a.m., according to Lt. Scott Dunn of the Sonoma County Sheriff's Department.

Boats and helicopters from county, state and federal agencies searched the ocean and shoreline but could not locate her.

"Ankle-deep water is enough to knock you down and, given the angles of some of these beaches, it's easy to be driven back into the water," Dunn told the San Francisco Chronicle. "People underestimate the power of waves."

It was the second incident this year in Sonoma County where a person trying to rescue a dog was swept into the ocean to their death. On Jan. 12, a 19-year-old woman was pulled into the ocean at Portuguese Beach. Her body was found three days later.